Phospholipid Bilayer

phospholipids are amphipathic(phobic and philic end) which causes layers to naturally form their bilayer structure. the philic heads are attracted to the extracellular water, the phobic tails are attracted to the intermembraneous grease

active transport

diffusion

concentration gradient

uneven distribution of particles, potential energy exists on the side with the higher concentration. spreads from an area of high concentration to an area of low concentration: moving down the concentration gradient. Once evenly distributed: particles move in a dynamic equilibrium

indirect active transport(co-transport, sodium glucose pump)

Co-transport

the active transport of a substance against its concentration gradient (low to high) by coupling its transport with the facilitated diffusion of another substance down its concentration gradient. Both Na+ and K+ travel through the same protein, but Na+ travels down the concentration gradient and glucose travels against its concentration gradient. It is active transport because energy was used earlier by the Na+ K+ pump to maintain a hight Na+ concentration in the extracellular environment. It is indirect active transport because a different protein had already used energy(ATP) to establish the right conditions for transport.

Cell Junctions (3 types)

Anchoring Junctions

1)Adhering Junctions: cement cells together, cadherins: proteins that lock together and connect to the microfillaments in the cytoskeleton 2) desmosomes: protein plaque "rivets", scattered along the sides of cells, abundant in cells under large amounts of mechanical stress

tight junctions

Gap Junctions

animal cells/ plasmodesmata in plant cells: donut shaped channels made of connexin proteins that allow cells to share small molecules and fluids; can twist to open and close channels "communication junctions" found in cells requiring synchronization such as heart muscle cells.